Automatic keying device



Patented June 30, 1942 AUTOMATIC KEYING DEVICE Irving F. Byrnes,Riverdale, N. Y., assignor to Radio Corporation of America, acorporation .of Delaware Application February 14, 1941, Serial No.378,881

2 Claims. (Cl. 17866) This invention relates to keying devices and moreparticularly to an arrangement for automatically keying a radiotransmitter which is used to send out distress signals. The invention,however, has other applications which may readil suggest themselves tothose skilled in the art.

It is an object of my invention to provide a system and a method forutilizing a direct current source to produce a periodic keying actionconsisting of circuit closures for definite periods of time separated byopen circuit conditions for other definite periods of time.

It is another object of my invention to provide apparatus including adirect current source, a converter for deriving an alternating currentfrom said direct current source, a synchronous or other constant speedmotor, and a keying device operable by said motor for alternatelyclosing and opening a circuit during periodically recurring timeintervals.

It is conventional practice in radio marine signaling systems to sendout a series of dash signals separated by spaces for the purpose oftransmitting a distress call. Certain automatic alarm responsive devicesare now standardized which will answer to a distress call consisting ofat least four dash signals of four seconds duration separated by spacingsignals of one second duration. Certain tolerances are made, however, inthe durations of the dashes and the spaces respectively so that manualkeying of the radio transmitter may be permissible. It is advantageous,however, to provide an automatic keying device which will moreaccurately determine the time intervals for the successive dashes andspaces in distress calls. Such a keying device is contemplated in theimprovements herein disclosed.

On ship board it would be desirable to use alternating current and asynchronous motor driven thereby for timing the dash and space intervalsof the distress call. The usual power supply system on board ship isnot, however, one of alternating current but of direct current.Furthermore, it frequently happens that when a ship is in distress itsentire power supply system is disabled. This, condition makes itdesirable to operate any radio or auxiliary apparatus by means ofstorage batteries, or batteries of other types. It is, therefore, afurther object of my invention to provide means for automatically keyinga radio transmitter in accordance with the requirements of internationaldistress calls, using only the power supply which is available from abattery.

Other objects and advantages of my invention will be appreciated uponreview of .the following detailed description in which the accompanyingdrawing is referred to. In the drawing the sole figure representsdiagrammatically a circuit arrangement and component elements incombination for producing certain new results.

The keying circuits I and la. may lead to the normal keying circuits ofone or more radio transmitters. These circuits are closeable by means ofa relay 2. The relay in turn is actuated by contact members 3 consistingpreferably of a pair of contact springs one of which is substantialiystationary, while the other is actuated by a rotating cam 4. Theperiphery of this cam is designed to open the contacts during one-fifthof a revolution, that is, for one second, and to close the contactsduring the remaining fourfifths of a revolution, or four seconds. Thepreferred rotational speed of the cam 4 is determined by a reducing gear5 and the speed of the synchronous motor 6.

Means are provided for converting the direct current from the batterysource 1 into alternating current, consisting of a vibrator 8 of more orless conventional type. This vibrator is provided with a winding 9 incircuit between one terminal of the battery I and a self-interruptingcontact arrangement shown at Ill, the other side of which leads back tothe battery. The armature of the vibrator 8 is mounted on a spring I! insuch manner as to have a definite vibration rate. When the winding 9 isunenergized, a circuit is closed from the battery I through the backcontact which takes current from the spring I and feeds it to one of thewindings in the synchronous motor 6. When the vibrator Winding 9 isenergized, the current from battery I is diverted through the frontcontact which then engages with the spring H and is thence fed toanother winding of the synchronous motor 6. The periodicity of thevibrations in the spring 9 is such as to set up periodic impulsesalternately directed into different windings of the synchronous motor 6.This motor may be provided with means for automatically starting thesame, or it may be provided with a knob on the end of its shaft formanually spinning it into synchronous speed.

In shunt with the self-interrupting contacts I0 I preferably provide acapacitor l2 for reducing the are on breaking the contacts ID. Adoublepole single-throw switch 13 may be provided for starting thekeying device when it is to be put in service. Fuses l4 may also beprovided as amatter of protection against the possibility of shortcircuits.

In the operation of my improved keying device it will be clear that itis only necessary to close the switch I3, see that the vibrator 8 startshumming, see that the synchronous motor 6 goes into operation andfinally to note that the keying operation itself is being properlyefiected. This last step in the operation may be noted by the flashingof a pilot light I6 which is in parallel with the relay winding 2'.

The invention is to be understood as not necessarily limited to theprecise details of the circuit arrangement and the combination elementsas herein shown and described. On the contrary, the scope of theinvention is limited only in accordance with the claims.

I claim:

1. In an automatic keying device for radiant energy transmission ofdistress signals, a source of direct current, a fixed frequency vibratorof the electro-magnetic type operable from said source, said vibratorhaving contact members arranged to alternately close two circuit pathsfrom one terminal of said source, an alternating current motor havingwindings connected to said circuit paths and to the other terminal ofsaid source, a reducing gear constituted by a worm driven by said motorand a gear driven by said worm, a cam rotatable by said reducing gear ata relatively slow angular velocity, said cam having a one-to-four ratiobetween the angles subtended by its maximum radius and its lesser radii,contact elements operable to an open-cit" cuit position by the camperiphery of maximum radius, and keying means including a relayenergizable by periodic closure of said contact elements, during therelatively long periods of such closure as compared with theopen-circuit periods.

2. In a device of the class described, a source of direct current, asubstantially constant frequency vibrator operable by current from saidsource to produce a double-path output of discrete current pulses, aconstant speed alternating current motor operable by said currentpulses, cam controlled switching means for keying at least one circuiton and off during predetermineo marking and spacing intervalsrespectively, said cam being of suitable shape to produce markingintervals substantially four times as long as the spacing intervals, anda reducing gear through which the cam of said switching means is drivenby said motor, said gear having a ratio such that the periodicity ofsaid marking and spacing intervals is of the order of several secondsper cycle compared with an interrupting frequency of said vibratoramounting to many current pulses per second.

IRVING F. BYRNES.

